The Embryo: Gene Regulation

Question 1

What is mitosis and what is it’s genetic information?

Answer 1

Daughter cells have genomes identical to parental cells
23 PAIRS of chromosomes
diploid [2n]

Question 2

What is meiosis and what is it’s genetic information?

Answer 2

formation of spermatocyte and oocyte

Each have 23 individual chromosomes (haploid 1n)

Chromosome crossover for genetic diversity

Chromosomes different from parents

Question 3

What is Spermatogenesis

Answer 3

No gene expression
chromosome condensation and repackaging
no organelles

Question 4

what is oogenesis

Answer 4

protein, RNA, etc. synthesis and accumulation

Organelle buildup

Question 5

What are the early cellular activities during development?

Answer 5

1. Cell proliferation
   Repeated cycles of S and M phases (increase in cell numbers not size)
2. Cell specialization
   differentiation into different cell types
3. Cell interactions
   cell-cell coordination in tissues
4. cell movement
   arrangement into structured tissues and organs

Question 6

What are the different potencies of stem cells?

Answer 6

totipotent - can differentiate into whole organism

pluripotent - can differentiate into most cells

multipotent - can differentiate into fewer related cells (adult stem cells)

Question 7

How are stem cells controlled?

Answer 7

By loss of telomeres

telomerase expressed in stem cells (shutoff during cell division)

Question 8

What is important about embryonic stem cells?

Answer 8

Pluripotent
DNA is unmethylated
Differentiate into adult stem cells

Question 9

What is important about adult stem cells?

Answer 9

Multipotent

Question 10

How do cells with the same genome become different?

Answer 10

Intercellular signaling

Signals from neighboring cells
Signals from cells outside the group
Changes in DNA transcription

Question 11

What are HOX genes?

Answer 11

Code for transcription factors (intracellular signalling)

Controls segmenting of body

Affect morphogens (specific position of cells)

Question 12

What is epigenetics?

Answer 12

Inheritance of phenotypic changes without changing nucleotide sequence of DNA (ex. methylation)

Question 13

What are the epigenetic changes during differentiation?

Answer 13

Rich CpG (or CG) at promoter sites
Methylated C to shut down expression
chromatin get more condensed
histone content changes

Question 14

What is Barr body?

Answer 14

Highly condensed heterochromatin
Result of X chromosome inactivation
reactivated in germ calls (removal of epigenetic markers)